Many image-forming apparatuses generate images from a corresponding set of pixels representing a digital color image. Such devices include printers that form images on a hardcopy media, displays that produce an image on a display screen, and projectors that project a digital image onto a surface, among many others. Each pixel has a value that specifies the color of the pixel—such as, for example, its hue, saturation, and lightness—in a color space. These devices typically use a plurality of different color colorants, such as a colored fluid or ink, or a colored light, to generate the desired color when rendering the image.
However, a portion of an image-forming device may become defective such that it is unable to generate the desired color for all of the pixels. For example, a component that produces a particular colorant may become defective. In a display or a projector that uses DLP technology, for example, a micro-mirror associated with a particular colorant may not operate properly. Similar effects can occur in other types of pixel-addressable displays, such as those used in televisions, digital cameras, cell phones, and the like.
Print mechanisms are widely used in a variety of products, such as printers, plotters, copiers, cameras, facsimile machines, and all-in-one devices (e.g. a combination of at least two of a printer, scanner, copier, and fax), to name a few. In a print mechanism, such as for example a mechanism that uses inkjet technology to generate a hardcopy print on a print medium, a defective print element for a particular colorant can emit drops that have a drop weight (which corresponds to the amount of the colorant) that is higher or lower than an acceptable range for producing high quality printed images. In some cases, the print element may fail to emit any drops at all.
When a defective component is used to print a raster, pixels in the raster that utilize the colorant that corresponds to the defective component can display an incorrect color. Often the difference in color is visible to the human eye at a normal viewing distance, which undesirably degrades the quality of the rendered image and can result in the image forming device being repaired or replaced, incurring increased cost and loss of time.